Linear tracking turntables, whatever happened?


Curious as to the demise and downfall of the seemingly short lived linear tracking TT.
Just from a geometry point of view I would have thought a linear arm should be superior to one with a fixed pivot that sweeps through an arc.
Obviously there is much more to it than that, sort of the reason for this thread.
I am genuinely interested in trying one out for myself as well.
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All this posting got me fiddling with my rabco  st 7 with a BO 20en Mmc. Been sitting 20 years it works but arm leads the notch tried adjusting it but have noticed the tracking wheel is a soft compound looks like it’s got grease in it  actually. Not sure if it’s degraded and I need to replace it or get it serviced but not sure where to turn to. Parts might not be available like to listen to my records again   Any suggestions are appreciated   Bob
Fairly sure early on in this thread when the Rabco was discussed that Ralph or Lew mentioned the tracking wheel is fairly common item needing replacement along with belts.
Might start there?
Yes I’m thinking it’s degraded searched eBay for parts but I have no other leads yet. Ty 
Right near the end of the TT era before CD's took over the Japanese made some very nice high end LT tables. I have several, a Technics SL-M3, a Yamaha PX-3 and a Pioneer PL-L1000. My favorite is the Technics SL-M3. Super specs for wow and flutter and it's really cool to watch the arm tracking in operation. It's true that the arm has to go off center a tiny amount before the drive pulls it back in line again. There is a feed motion on the arm about once per revolution so since the grooves are about 0.003 to 0.004 of an inch apart it is never more that that far from being perpendicular from the groove. I don't think anything tracks that close and since the arm pivots it never loads the cantilever. Think about that, the stylus moves 0.003 of an inch towards the center and the tone arm is driven towards the center by a like amount.
These units were very expensive in the day and CDP were taking the world by storm. The three units above were the last hurrah by the Japanese before giving up on TT manufacturing. Find one of these units and have it serviced for years of trouble free operation.
There is nothing inherently wrong with LT TT, they were just introduced to late in the game. Technically they are much better that a swinging tone arm that spends most of it's time way out of alignment.
BillWojo
I did some surfing on the web and the tracking roller is a rubber o ring 3/8  Id 11/32 od  mounted on a  metal wheel  saw a posted picture of it. Mine has turned to mush so with some patience and luck and great advice from audio gear heads I will fix. It  thx